A silver complex with tryptophan: Synthesis, structural characterization, DFT studies and antibacterial and antitumor assays in vitro Marcos A. Carvalho a , Raphael E.F. de Paiva a , Fernando R.G. Bergamini a , Alexandre F. Gomes a , Fábio C. Gozzo a , Wilton R. Lustri b , André L.B. Formiga a , Silvia M. Shishido c , Carmen V. Ferreira c , Pedro P. Corbi a,⇑ a Institute of Chemistry, University of Campinas – UNICAMP, P.O. Box 6154, 13083-970 Campinas, SP, Brazil b Biological and Health Sciences Department – UNIARA, 14801-320 Araraquara, SP, Brazil c Laboratory of Bioassays and Signal Transduction, Department of Biochemistry, Institute of Biology, University of Campinas – UNICAMP, P.O. Box 6109, 13083-970 Campinas, SP, Brazil highlights " A silver(I) complex with tryptophan. " IR, ESI-QTOF-MS and NMR studies permitted proposing nitrogen and oxygen coordination. " DFT studies supported the proposed structure for the complex. " The compound shows antibacterial activities against Gram-negative and -positive bacteria. " The complex was cytotoxic in vitro against human pancreatic carcinoma and melanoma cells. article info Article history: Received 6 June 2012 Received in revised form 19 July 2012 Accepted 24 July 2012 Available online 2 August 2012 Keywords: L-tryptophan Silver Solid-state NMR ESI-QTOF mass spectrometry Antibacterial agent Antitumoral assays abstract The synthesis, spectroscopic characterization and biological assays of a new silver(I) complex with L-tryp- tophan (TRP) are presented. Elemental and thermal analyses and ESI-QTOF mass spectrometric measure- ments of the solid compound suggest the composition AgC 11 H 11 N 2 O 2 . Infrared and solid-state NMR analyses indicate coordination of TRP to Ag(I) ion through the nitrogen of the NH 2 group and also through the oxygen of carboxylate group. Theoretical (DFT) calculations permit proposing an optimized geometry for the complex. Antibacterial assays indicated that the Ag-TRP complex is effective against Staphylococ- cus aureus and Enterococcus faecalis (Gram-positive), and Pseudomonas aeruginosa and Escherichia coli (Gram-negative) bacterial strains. The complex was also cytotoxic against Panc-1 (human pancreatic car- cinoma) and SK-Mel 103 (human melanoma) cells. Ó 2012 Elsevier B.V. All rights reserved. 1. Introduction The earliest reports on the therapeutic uses of transition metal complexes in medicine date from the 16th century. In the late 1960s, the antitumor activities of cisplatin, or cis-diamminedi- chloridoplatinum(II), were reported by Rosenberg. In the 1970s, cisplatin started to be used worldwide against several types of can- cer, principally testicular, ovarian, head and neck cancers [1]. The successful application of cisplatin led to the syntheses and antitu- moral assays of several metal complexes, including those of gal- lium, germanium, tin, bismuth, titanium, ruthenium, rhodium and iridium, molybdenum, copper, silver, palladium, and gold. Some of these complexes were shown to be effective against hu- man and animal tumors in vitro [2,3]. 0022-2860/$ - see front matter Ó 2012 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.molstruc.2012.07.044 Abbreviations: Ag-TRP, Ag(I) complex with tryptophan; ATCC, American type collection cell; B3LYP, Becke 3-Lee Young Parr functional; BHI, brain-heart infusion medium; CFU, colony forming unit; CRO, ceftriaxone; DFT, density functional theory; DMEM, Dulbelcco’s modified eagle’s medium; DMSO, dimethylsulfoxide; ESI-QTOF-MS, electrospray ionization quadrupole time-of-flight mass spectrome- try; GEN, gentamicine; IR, infrared; KOH, potassium hydroxide; LANL2DZ, Los Alamos National Laboratory – 2nd version on double zeta function; MIC, minimum inhibitory concentration; MH, Mueller–Hinton agar; MTT, (3-(4,5-dimethylthiazol- 2-yl)-2,5-diphenyl tetrazolium bromide; NMR, nuclear magnetic resonance; PCM, polarized continuum model; PES, potential energy surface; SSNMR, solid-state nuclear magnetic resonance; SUAHF, simplified united atomic radii; TD-DFT, time dependent density functional theory; TGA/DTA, thermogravimetric and differential thermal analyses TGA/DTA; TRP, L-tryptophan; UV–Vis, Ultraviolet–Visible spectroscopy. ⇑ Corresponding author. Tel.: +55 19 35213130; fax: +55 19 35213023. E-mail addresses: ppcorbi@iqm.unicamp.br, pedrocorbi@yahoo.com (P.P. Corbi). Journal of Molecular Structure 1031 (2013) 125–131 Contents lists available at SciVerse ScienceDirect Journal of Molecular Structure journal homepage: www.elsevier.com/locate/molstruc